Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 300142
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST MON JUN 29 2015

.SYNOPSIS...
LIGHT WINDS WILL LEAD TO LOCAL AFTERNOON SEA BREEZE AND NIGHTTIME
LAND BREEZE FOR THE NEXT FEW DAYS. LOW CLOUDS AND SHOWERS WILL FAVOR
THE INTERIOR AND LEEWARD SECTIONS EACH AFTERNOON AND EVENING. NIGHTS
AND MORNINGS WILL BE GENERALLY CLEAR...THOUGH A FEW SHOWERS MAY
LINGER OVER WINDWARD SECTIONS. INCREASING SHOWERS MAY OCCUR AROUND
MID-WEEK OVER THE BIG ISLAND AS A BATCH OF TROPICAL MOISTURE PASSES
SOUTH OF THE AREA.

&&

.DISCUSSION...
WATER VAPOR IMAGERY SHOWS AN UPPER LEVEL TROUGH OVER THE STATE...
WITH ANOTHER SHORTWAVE FAR TO THE NORTH-NORTHWEST. THE SUBTROPICAL
JET IS LOCATED NEAR THE BIG ISLAND ON THE SOUTHEAST SIDE OF THE
TROUGH. AT THE SURFACE...A WEAK TROUGH IS LOCATED JUST NORTH OF THE
STATE...WITH A NEARLY STATIONARY FRONT FARTHER TO THE NORTH. SURFACE
HIGHS ARE LOCATED TO THE NORTHEAST AND NORTHWEST OF THE STATE...
GENERALLY ALONG 30N. ANOTHER SURFACE TROUGH IS ALSO LOCATED SEVERAL
HUNDRED MILES SOUTHEAST OF THE BIG ISLAND. 00Z SOUNDINGS FROM HILO
AND LIHUE SHOW INVERSIONS OF 7-8KFT AND PRECIPITABLE WATERS OF
1.1-1.2 INCHES. EARLY AFTERNOON MIMIC TOTAL PRECIPITABLE WATER
IMAGERY SHOWS AN AREA OF SOMEWHAT DRIER AIR FROM KAUAI TO THE BIG
ISLAND...WITH MUCH HIGHER VALUES JUST SOUTHEAST AND EAST OF THE BIG
ISLAND.

AFTERNOON CLOUDS AND SHOWERS ARE AGAIN MOST ACTIVE ACROSS KAUAI AND
OAHU...ESPECIALLY ALONG THE WINDWARD SIDE OF THE KOOLAU RANGE.
RAINFALL AMOUNTS HAVE BEEN UP TO HALF AN INCH DURING THE PAST 12
HOURS HERE...THOUGH WITH A COUPLE RECENT RAINFALL ALERTS FOR RATES
OF 1 INCH PER HOUR. RAINFALL HAS BEEN A QUARTER INCH OR LESS ACROSS
MAUI COUNTY AND THE BIG ISLAND. WITH LAST EVENING AS AN EXAMPLE...
WILL HOLD ONTO SHOWERS FOR LONGER INTO THE EVENING ESPECIALLY ACROSS
WINDWARD OAHU...BUT THEN CLOUDS WILL EVENTUALLY CLEAR OUT DUE TO
DEVELOPING LAND BREEZES. SURFACE PRESSURES ACROSS THE STATE HAVE
DROPPED ABOUT A MILLIBAR IN THE PAST 24 HOURS...AND THE PRESSURE
DIFFERENCE BETWEEN BUOY 51101 TO THE NORTHWEST OF THE STATE AND
51002 TO THE SOUTH HAS DROPPED BY ABOUT HALF A MILLIBAR OVER THE
SAME TIME PERIOD. WITH THIS WEAKENING PRESSURE GRADIENT AND OVERALL
DRYING ACROSS THE SMALLER ISLANDS...LAND BREEZES WILL HELP TO CLEAR
OUT MOST AREAS OVERNIGHT...AT LEAST ACROSS THE SMALLER ISLANDS. THE
INCREASE IN MOISTURE FROM THE SOUTHEAST WILL ENHANCE SHOWERS ACROSS
THE BIG ISLAND TONIGHT...AND PERHAPS ACROSS EASTERN HALEAKALA LATE
AS WELL.

THE SHORTWAVE TROUGH CURRENTLY NOTED NORTHWEST OF THE STATE WILL
HELP TO FURTHER AMPLIFY THE UPPER LEVEL TROUGH OVER THE ISLANDS.
FORECAST SOUNDINGS SHOW INVERSIONS WEAKENING THROUGH TUESDAY
NIGHT...AND NEARLY ERODING COMPLETELY OVER THE WESTERN HALF OF THE
STATE. THE GRADIENT IS ALSO EXPECTED TO REMAIN WEAK AS THE SURFACE
COL TO OUR NORTH SHIFTS SOUTHWARD. THIS KEEPS WINDS LIGHTEST NEAR
KAUAI...WITH SLIGHTLY STRONGER WINDS FARTHER SOUTHEAST. THE GENERAL
CONSENSUS OF THE 12Z RUNS IS TO KEEP A WEAKLY/BROADLY DEFINED TROUGH
NEAR THE STATE...WITH EAST-SOUTHEAST FLOW OVER THE EASTERN HALF OF
THE STATE AND WEAK BUT GENERAL EAST-NORTHEAST OR NORTHEAST FLOW OVER
THE WESTERN HALF. THERE SHOULD BE ENOUGH OF A GRADIENT OVER THE
EASTERN HALF OF THE STATE TO MAINTAIN LIGHT TRADE WINDS ACROSS
WINDWARD SECTIONS...LEADING TO A FEW CLOUDS AND SHOWERS AT NIGHT
DESPITE INCREASINGLY WIDESPREAD LAND BREEZES ELSEWHERE. THE SURFACE
TROUGH CURRENTLY SOUTHEAST OF THE BIG ISLAND WILL TRACK WESTWARD
WELL TO OUR SOUTH...THOUGH A FAIR AMOUNT OF TROPICAL MOISTURE IS
POOLED ALONG IT. SOME OF THIS MOISTURE WILL BRUSH THE STATE
TONIGHT...THOUGH THE GFS ALSO SHOWS ANOTHER SURGE OF MOISTURE LATE
WEDNESDAY INTO THURSDAY...WHICH MAY ALSO AFFECT THE SMALLER ISLANDS
AS WELL.

DURING THE SECOND HALF OF THE WEEK...BOTH THE 12Z GFS AND ECMWF SHOW
THE SURFACE RIDGE STRENGTHENING EAST OF THE STATE BUT A FRONT
STALLING TO THE NORTHWEST. THIS PATTERN WOULD LEAD TO A GRADUAL
STRENGTHENING TO THE WINDS...AT LEAST OVER THE EASTERN HALF OF THE
STATE. DEPENDING ON HOW THE LINGERING SURFACE TROUGH NEAR THE STATE
EVOLVES...KAUAI MAY REMAIN IN A LIGHTER WIND PATTERN THROUGH MUCH OF
THE WEEK. FOR LATE IN THE WEEK AND INTO NEXT WEEKEND...EXTENDED
MODELS SHOW THE SURFACE RIDGE GRADUALLY SHIFTING NORTHWARD...
PROVIDING A RETURN TO DEEPER/MORE CONSISTENT TRADE WINDS FOR THE
ISLANDS...THOUGH STILL MORE DUE EASTERLY THAN NORMAL.

&&

.AVIATION...
WEAK TRADE WINDS WILL CONTINUE ACROSS THE ISLANDS DUE TO A WEAK
TROUGH LYING NEAR AND JUST NORTH OF THE STATE. THE LIGHT WINDS WILL
TEND TO YIELD TO SEA BREEZES DURING THE DAYTIME HOURS AND LAND
BREEZES AT NIGHT. EXPECT WIDESPREAD VFR CONDITIONS MAINLY FROM LATE
EVENING TO MID MORNING HOURS. AFTERNOON CONVECTION WILL PRODUCE ISOL
MVFR CIGS AND SHRA MAINLY OVER THE SLOPES AND INTERIOR PARTS OF THE
ISLANDS. THESE AFTERNOON CLOUDS WILL DISSIPATE NEAR OR JUST PAST
SUNSET. SIMILAR CONDITIONS EXPECTED THROUGH TUESDAY.

&&

.MARINE...
SMALL CRAFT ADVISORY CONDITIONS ARE NOT EXPECTED THROUGH THE
WEEK...AND PERHAPS NOT UNTIL LATE IN THE WEEKEND. THE BARBERS POINT
BUOY SHOWS THE DIMINISHING SOUTH SWELL MAY HAVE BOTTOMED OUT...WITH
SMALL ENERGY THE NEXT INCREASE STARTING TO SHOW UP. WAVEWATCH SHOWS
A SERIES OF SMALL TO MODERATE SOUTH-SOUTHWEST SWELLS THROUGH THE
WEEK. THE LIGHT BACKGROUND EAST TO SOUTHEAST FLOW WILL KEEP SHORT
PERIOD WIND SWELL BELOW TYPICAL SUMMERTIME HEIGHTS. FINALLY...A
SMALL...OUT OF SEASON NORTHWEST SWELL IS EXPECTED TO ARRIVE LATE
WEDNESDAY NIGHT...PEAK THURSDAY...AND SLOWLY DIMINISH FRIDAY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

DISCUSSION/MARINE...BRAVENDER
AVIATION...FUJII




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